You may be attempting to send mail from a system which is being blocked
for cause. System administrators should consider the current most
common causes of blocking.

Misdirected auto replies:
Vacation messages, auto-responses, challenge-response spam filters and
virus-notification messages are some of the most prominent examples
of automatic emails which have caused otherwise innocent sites to be
blocked. If you or your system's administrator operate any of these
systems, they may be responsible for your system being blocked.
More details..

SMTP-auth brute-force password guessing:
Microsoft Exchange and other servers using smtp-auth to limit outbound
mail are being exploited frequently in the wild. Spammers are using
brute-force methods to find valid accounts. Today, the holes found by spammers
are much more subtle than the traditional "open relay."
More details..

"Typhoid Mary" laptops:
Sometimes, normally well-defended networks can become spam sources when
travelling users connect systems which have been infected outside your
network are connected. Check your mailserver logs and firewall logs for
unusually large amounts of email from a single internal IP address.

SpamCop Blocking List Details

The SpamCop Blocking List (SCBL) lists IP addresses which have
transmitted reported email to SpamCop users. SpamCop, service providers
and individual users then use the SCBL to block and filter unwanted
email. The SCBL is a fast and automatic list of sites sending reported
mail, fueled by a number of sources, including automated reports and
SpamCop user submissions. The SCBL is time-based, resulting in quick
and automatic delisting of these sites when reports stop.

Start by following the link(s) in the email report you received from
SpamCop. These links provide details about the reported email and SpamCop's
procedures. These links provide access to advanced options for
analyzing and responding to reported spam.

The SCBL aims to stop most spam while not blocking wanted email.
This is a difficult task. It is not possible for any blocking tool to
avoid blocking wanted mail entirely. Given the power of the SCBL,
SpamCop encourages use of the SCBL in concert with an actively
maintained whitelist of wanted email senders. SpamCop encourages SCBL
users to tag and divert email, rather than block it outright. Most SCBL
users consider the amount of unwanted email successfully filtered to
make the risks and additional efforts worthwhile.

The SCBL is aggressive and often errs on the side of blocking mail.
When implementing the SCBL, provide users with the information about
how the SCBL and your mail system filter their email. Ideally, they
should have a choice of filtering options. Many mailservers operate
with blacklists in a "tag only" mode, which is preferable in many
situations.

There is no warranty associated with using this system. It is
provided as is.